The Curtiss P-36 Hawk, also known as the Curtiss Hawk Model 75, is an American-designed and built fighter aircraft of the 1930s and 40s.
A contemporary of the Hawker Hurricane and Messerschmitt Bf 109, it was one of the first of a new generation of combat aircraft—a sleek monoplane design with a retractable undercarriage making extensive use of metal in its construction.
Perhaps best known as the predecessor of the Curtiss P-40 Warhawk, the P-36 saw little combat with the United States Army Air Forces during World War II.
It was the fighter used most extensively and successfully by the French Air Force during the Battle of France.
The P-36 was also ordered by the governments of the Netherlands and Norway but did not arrive in time to see action before both were occupied by Nazi Germany.
The type was also manufactured under license in China, for the Republic of China Air Force, as well as in British India, for the Royal Air Force (RAF) and Royal Indian Air Force (RIAF).
Axis and co-belligerent air forces also made significant use of captured P-36s.
Following the fall of France and Norway in 1940, several dozen P-36s were seized by Germany and transferred to Finland; these aircraft saw extensive action with the Finnish Air Force against the Soviet Air Forces.
The P-36 was also used by Vichy French air forces in several minor conflicts; in one of these, the Franco-Thai War of 1940–41, P-36s were used by both sides.
From mid-1940, some P-36s en route for France and the Netherlands were diverted to Allied air forces in other parts of the world.
The Hawks ordered by the Netherlands were diverted to the Dutch East Indies and later saw action against Japanese forces.
French orders were taken up by British Commonwealth air forces, and saw combat with the South African Air Force (SAAF) against Italian forces in East Africa, and with the RAF over Burma.
Within the Commonwealth, the type was usually referred to as the Curtiss Mohawk.
With around 1,000 aircraft built by Curtiss, the P-36 was a commercial success for the company.
It also became the basis of the P-40 and two unsuccessful prototypes: the P-37 and the XP-42.
The Curtiss Model 75 was a private venture by the company, designed by former Northrop Aircraft Company engineer Don R. Berlin.
The first prototype, constructed in 1934, featured all-metal construction with fabric-covered control surfaces, a Wright XR-1670-5 radial engine developing 900 hp (670 kW), and typical United States Army Air Corps armament of one .30 in (7.62 mm) and one .50 in (12.7 mm) machine gun firing through the propeller arc.
Also typical of the time was the total absence of cockpit armour or self-sealing fuel tanks.
The distinctive landing gear, which rotated 90° to fold the main wheels flat into the thin trailing portion of the wing, resting atop the lower ends of the maingear struts when retracted, was a Boeing-patented design for which Curtiss had to pay royalties.
The prototype first flew on 6 May 1935, reaching 281 mph (452 km/h) at 10,000 ft (3,000 m) during early test flights.
On 27 May 1935, the prototype was flown to Wright Field, Ohio, to compete in the USAAC fly-off for a new single-seat fighter, but the contest was delayed because the Seversky entry crashed on its way there.
Curtiss took advantage of the delay to replace the unreliable engine with a Wright XR-1820-39 Cyclone producing 950 hp (710 kW) and to rework the fuselage, adding the distinctive scalloped rear windows to improve visibility.
The new prototype was designated Model 75B with the R-1670 version retroactively designated Model 75D.
The fly-off finally took place in April 1936.
Unfortunately, the new engine failed to deliver its rated power and the aircraft only reached 285 mph (459 km/h).
Although the competing Seversky P-35 also underperformed and was more expensive, it was still declared the winner and awarded a contract for 77 aircraft.
However, on 16 June 1936, Curtiss received an order from USAAC for three prototypes designated Y1P-36.
The USAAC was concerned about political turmoil in Europe, and about Seversky’s ability to deliver P-35s in a timely manner, and therefore wanted a backup fighter.
The Y1P-36 (Model 75E) was powered by a 900 hp Pratt & Whitney R-1830-13 Twin Wasp engine, and the scalloped rear canopy was further enlarged.
The new aircraft performed so well that it won the 1937 USAAC competition with an order for 210 P-36A fighters.
The aircraft’s extremely low wing loading of just 23.9 lb/ft2 gave it outstanding turning performance, and its high power-to-weight ratio of 0.186 hp/lb gave superb climbing performance for the time.
The single speed supercharger was a serious handicap at high altitudes.
Compared to the later Allison-engined P-40, the P-36 shared the P-40’s traits of excellent high-speed handling, roll rate that improved at high speed, and relatively light controls at high speed.
However, it was underpowered, affecting its acceleration and top speed, and it did not accelerate in a dive as well as the P-40.
Variants
Model 75A
Company-owned demonstrator aircraft flown with several engine fits
Model 75B
Prototype with Wright R-1820 radial engine
Model 75D
First prototype, Wright Whirlwind R-1670 radial
Model 75H
Internal company designation for a simplified export version with fixed landing gear, two slightly differing aircraft built, first sold to China, second to Argentina
Model 75I
Company designation for the P-37.
Model 75J
Company-owned 75A temporarily fitted with an external supercharger
Model 75K
Unbuilt version, intended to use the Pratt & Whitney R-2180 Twin Hornet radial.
Model 75P
Production P-36A (serial 38-010) fitted with Allison V-1710 liquid-cooled engine, prototype for Curtiss P-40
Model 75R
Company-owned 75A temporarily fitted with R-1830-SC2-G with turbo-supercharger, attained 330 mph (530 km/h) but proved complex and unreliable
Model 75S
Company designation for the P-42
Y1P-36 (Model 75E)
USAAC prototype, Pratt & Whitney R-1830
P-36A (Model 75L)
USAAC version
P-36B
Production P-36A fitted with an R-1830-25 producing 1,100 hp (820 kW), reached 313 mph (504 km/h), returned to original P-36A configuration
P-36C
An additional 0.30 in machine gun installed in each wing with external ammunition boxes under the wings, R-1830-17 of 1,200 hp (890 kW); last 30 production aircraft were completed as P-36Cs
XP-36D
Production P-36A modified with two .50 in (12.7 mm) machine guns in the nose and four 0.30 in machine guns in the wings
XP-36E
Production P-36A armed with four 0.30 in machine guns in the wings, retained standard fuselage guns
XP-36F
Production P-36A fitted with two 23 mm (0.91 in) Madsen autocannons under the wings, reverted to P-36A because guns imposed an unacceptable performance penalty with top speed of only 265 mph (426 km/h).
P-36G
Hawk 75A-8 used by Norway for training in Canada; later delivered to Peru. R-1820-G205A of 1,200 hp.
Hawk 75A-1
First production batch for France, four 7.5 mm (0.295 in) machine guns, R-1830-SC-G of 900 hp (670 kW); 100 built
Hawk 75A-2
Second production batch for France, either R-1830-SC-G or 1,050 hp (780 kW) R-1830-SC3-G, six 7.5 mm machine guns; 100 built
Hawk 75A-3
Third production batch for France, similar with Hawk 75A-2; 135 built (133 delivered).
Hawk 75A-4
Last production batch for France, Hawk 75A-2 with Wright R-1820-G205A Cyclone radial with 1,200 hp: 285 built, 81 delivered to France; others to Great Britain as Mohawk IV
Hawk 75A-5
Similar to Hawk 75A-4. Built under license in China (production was later moved to India), absorbed into RAF as Mohawk IV
Hawk 75A-6
Version for Norway; aircraft captured during the German invasion were eventually sold to Finland.
Hawk 75A-7
Version for Netherlands East Indies: 1,200 hp Cyclone, one .5 in (12.7 mm) and one .303 in (7.7 mm)in cowl and two .303 in (7.7 mm)in wings; later four .303 in (7.7 mm) (two in nose, one in each wing) and six 50 lb (23 kg) bombs.
Hawk 75A-8
Export version for Norway.
Later redesignated P-36G.
Hawk 75A-9
10 aircraft delivered to Persia, captured still in crates and used by RAF in India as Mohawk IVs
Hawk 75M
Simplified version with fixed landing gear and Wright R-1820 Cyclone for China, built by both Curtiss and Central Aircraft Manufacturing Company in China
Hawk 75N
Simplified version for Siam (Thailand) with non-retractable landing gear and wheel pants.
Hawk 75O
Simplified version for Argentina, 30 built and delivered by Curtiss with additional 200 to be built under license locally by Fabrica Militar de Aviones, however only 20 were completed.
Hawk 75Q
Two additional simplified demonstrators for China.
At least one is reputed to have been given an armament similar to that of the XP-36F and to have engaged in combat over Shanghai during the Japanese attacks in September 1937, reportedly shooting down several bombers before being brought down with the loss of the American pilot.
XP-37
Allison V-1710 inline, cockpit moved to the rear of the fuselage
YP-37
Service test version of XP-37, 13 built
XP-40
Allison V-1710 inline, prototype of the Curtiss P-40 Warhawk, one converted from a P-36A
XP-42
Testbed for streamlining cowlings around air-cooled engines.
